PROJECT SUMMARY Schools are an accessible and ecologically valid setting for children with ADHD to receive evidence-based interventions to reduce symptoms and improve functioning. Behavioral classroom management interventions are well-established treatments for elementary-school age children with ADHD. Randomized trials of behavioral classroom management interventions demonstrate that they decrease disruptive behavior symptoms and improve academic outcomes for children with ADHD. Teachers' implementation of these practices is often lower than recommended standards. Our preliminary work suggests that in the demanding context of under-resourced public schools, even when teachers intend to implement EBPs, they often struggle to do so. As such, it is important to understand and target both factors that promote teachers' intentions to implement EBPs, as well as those that promote their ability to act on their intentions. This K23 application proposes to iteratively develop and pilot test a set of key implementation strategies that promote teachers' implementation of behavioral classroom interventions for children with symptoms of ADHD. The research plan will address three specific aims: (1) Use observations, interviews, and surveys to examine malleable determinants of teachers' use of behavioral classroom interventions for children with ADHD symptoms; (2) Partner with community stakeholders to iteratively develop and refine a resource package of key implementation strategies to promote teacher use of behavioral classroom management interventions; (3) Pilot test the implementation strategy resource package to demonstrate feasibility in a small-scale Type 3 Hybrid Trial. The primary outcomes of the pilot study will be acceptability, appropriateness and feasibility, observed teacher use of behavioral classroom management interventions, and child ADHD symptoms and functional impairment. The research proposal supports a training plan to increase the PI's expertise in three areas: (1) School-based interventions for ADHD; (2) Developing tailored implementation strategies using mixed-methods; and (3) School-based hybrid implementation-effectiveness trials.